1. Field of the Invention
Aspects of the present invention relate to an additive for an electrolyte of a lithium secondary battery, an organic electrolyte solution including the additive, and a lithium battery using the electrolyte solution.
2. Description of the Related Art
Batteries are used as power sources for portable electronic devices, such as video cameras, cell phones, and notebook computers. Rechargeable lithium batteries have 3 times the energy density per unit weight, as compared to a conventional lead storage battery, nickel-cadmium battery, nickel-hydrogen battery, nickel-zinc battery, or the like. Rechargeable lithium batteries can also be rapidly charged.
Lithium batteries operate at a high driving voltage, and thus, a water-based electrolyte solution having a high reactivity with lithium cannot be used therein. Generally, an organic electrolyte solution is used for lithium batteries. An organic electrolyte solution is prepared by dissolving a lithium salt in an organic solvent. Organic solvents are stable under high voltages and preferably have a high ion conductivity, a high dielectric constant, and a low viscosity.
When a carbonate-based, polar, non-aqueous solvent is used in an electrolyte solution of a lithium battery, an irreversible reaction occurs, which uses an excessive amount of charge, due to a side reaction between a carbon anode and the electrolyte solution, during an initial charging. Due to the irreversible reaction, a passivation layer, such as a solid electrolyte interface (SEI), is formed on the surface of the anode. The SEI prevents the degradation of the electrolyte solution during charging/discharging, and acts as an ion tunnel. The SEI is selectively permeable to lithium ions and is impermeable to the organic solvent. Since only lithium ions are intercalated into the carbon anode (the organic solvent is not intercalated), the collapse of the carbon anode structure is prevented. When a metal-based active material, such as silicon, is used as an anode active material for a lithium battery, a volume change of the anode is increased during the charging/discharging of the battery. The SEI must be able to withstand such a volume change, while at the same time suppressing the degradation of the electrolyte solution, during the charging/discharging.